Hybrid occupant detection system

Abstract

An occupant detection system includes a detection electrode provided in a vehicle seat, a phase difference measuring unit, a direct current measuring unit, and a detecting unit that detects an occupant. The phase difference measuring unit supplies a reference signal comprising a sinusoidal wave to the detection electrode via a resistive element, detects the potential of the detection electrode as an electrode signal, and measures a phase lag time of the electrode signal relative to the reference signal. The direct current measuring unit applies a steady DC voltage to the detection electrode via a resistive element, detects the potential of the detection electrode, and measures time it takes from start of application of the DC voltage to the time when the detection electrode reaches a given potential, as a charge time. The detecting unit detects an occupant based on the phase lag time and the charge time.

Description

[0001]The disclosure of Japanese Patent Application No. 2010-055040 filed on Mar. 11, 2010 including the specification, drawings and abstract is incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The invention relates to an occupant detection system for detecting if an occupant is present in a vehicle seat, and more particularly to an occupant detection system that is able to detect an occupant with stability even when the vehicle seat is wet, for example.[0004]2. Description of the Related Art[0005]In automobiles, detected information as to whether an occupant is present in a seat is used for determining whether an air bag is to be deployed or inflated. A vehicle air-bag system is controlled so that an air bag deploys when an occupant is present in a seat, such as a passenger's seat, at the time of a collision of the vehicle, and the air bag does not deploy when no occupant is present in the seat. Also, in the case where...

AI Technical Summary

Benefits of technology

[0015]The conductive cloth may be a woven fabric into which conductive fibers are woven at fixed intervals. In this case, the occupant detection system is advantageous in the use of the detection electrode that is excellent in terms of durability and cost efficiency or economy.

[0016]The phase difference measuring unit may include a first comparator circuit that produces a binary reference phase signal by comparing the voltage of the reference signal with a predetermined threshold value, and a second comparator circuit that produces a binary electrode phase signal by comparing the electrode signal with a second threshold value. The second threshold value is set so that a phase of the reference signal at a point at which the reference signal passes the first threshold value is substantially the same as that of the electrode signal at a point at which the electrode signal passes the second threshold value. In this case, the timing or points in time at which the reference signal and the electrode signal reach substantially the same phase can be detected using a simple circuit. Then, a rise delay time and a fall delay time of the electrode phase signal relative to the reference phase signal are measured, as the phase delay time, so that processing corresponding to the phase difference can be easily performed.

[0017]The electrode signal may be produced as a signal having substantially the same amplitude as that of the reference signal, and the first co

Problems solved by technology

If an electric field is generated around the detection electrode, disturbances arise in the electric field when an occupant is seated in the seat.

Therefore, if the seat gets wet, the impedance around the detection electrode(s) may change, or a wet portion may act as an antenna, which may result in a problem that a determination as to the presence of a seated occupant or whether the occupant is an adult or a child is erroneously made.

However, in a condition where the back and head of the occupant are not in contact with the seatback of the seat, the system may not be able to accurately discriminate between an adult and a child.

Also, a large number of electrodes need to be installed in the seatback portion of the seat, and a switching circuit, or the like, for selectively using the electrodes needs to be provided, thus maki

Images